Under what circumstances should a group of motorcyclists ride in a single file?

Riding in a single file is essential for maintaining safety and visibility, especially in situations where road conditions or traffic demand more caution. When entering a freeway, motorcyclists should ride in a single file to allow for merging and to reduce the risk of collisions with other vehicles. This formation helps ensure that each rider has adequate space and reduces the chances of sudden lane changes that could be dangerous in crowded traffic scenarios.

Similarly, when crossing intersections, riding in a single file enhances safety by minimizing the width of the motorcycle group, allowing vehicles approaching from different directions to see and gauge the presence of the motorcyclists more easily. This positioning can help prevent accidents by making the group more visible and easier for other drivers to navigate around.

While riding in a single file on a straight road can also be safe and appropriate, it is not as critical as when entering freeways or crossing intersections, where traffic dynamics change significantly. Therefore, the correct circumstances for riding in a single file are specifically highlighted in the options that relate to freeway entries and intersections.